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1 October 2020

How we test robot lawn mowers

Learn how our robust lab tests separate the fantastic Best Buy robot lawn mowers from those you should avoid.
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We run a range of detailed, independent tests to discover the best robot lawn mowers and see how they cope with challenging mowing tasks.

Alternatively, head straight to our robot lawn mower reviews.

How well does it cut the grass?

We test each robot lawn mower on a range of grass types over a period of four weeks, assessing the efficiency of the cut and the neatness of the finish. This way we can compare how well the mower cuts over time as well as at first.

We see how well each robot mower handles long grass, rough grass, damp grass and a standard lawn, as well as how long it runs and charges for on average.

Several of our testers rate the mower’s grass cutting ability on the overall appearance of two lawns it has cut of each type, the evenness and cleanness of the cut, how many spots it misses, and any wear marks the wheels or blades leave behind.

For a detailed explanation of how robot lawn mowers work and their pros and cons, head to our guide on what is a robot lawn mower.

How evenly does it spread grass cuttings?

Unlike conventional lawn mowers, robot lawn mowers don't collect up the grass cuttings.

Instead, robot mowers finely chop the clippings and redistribute them on the lawn in a thin layer that gives it nutrients and keeps it healthy. This process is called mulching.

The best robot mowers will cut the grass into small bits and distribute them in an even layer. You’ll want to avoid robots that struggle to chop grass properly or leave clumps of cut grass, as when the clumps decompose they can cause your grass to rot.

We also test manual lawn mowers with mulching modes, and rate them for the quality and ease of using mulching modes.

If you're looking for a conventional lawn mower instead, head to our lawn mower reviews to see which ones we recommend.

Is it easy to set up and program?

The best robot lawn mowers are easy to set up and program, from laying the boundary wire, setting it to run for the first time, and connecting it up to any accompanying apps.

  • We assess how easy it is to construct any boundary wires and pegs to establish the mowing area.
  • We check how straightforward it is to use the iOS or Android smartphone apps to program the mowers to run at certain times each day or week, and how well you can keep track of its performance.
  • The convenience of using any manual controls, setting up the base station, setting the cutting height, lifting and carrying, changing the blades and cleaning the mower are all assessed.
  • Finally, we note any important limitations or interesting features the robot mowers have, like the total number of zones you can program it to mow, the maximum size lawn you can cut, and the presence of temperature and rain sensors.

Our overall convenience and construction ratings also take into account the feedback of our gardening experts.

Check the test results page of our robot lawn mower reviews to see which robots are the best in use. Our helpful guide on lawn care shares top tips on keeping your lawn looking its best.

Can the robot mower handle difficult terrain and obstacles?

Your robot mower is sure to frustrate you if it gets stuck whenever it hits an obstacle or a patch of uneven ground, which is why we test them in a range of difficult scenarios to see how well they can cope.

We run each mower around areas with fences, flowerbeds, patios, trees and narrow passages, and assess how well it navigates each.

Some mowers will smartly avoid obstacles and handle slopes and uneven ground without difficulty, whereas others will get stuck and need you to go and lift it up to get it out of trouble.

Head to our robot lawn mower reviews to see which models will smartly navigate whatever difficult terrain your garden might have.

Can I replace the battery?

Lithium-ion batteries always deplete and eventually die over time, and at Which?, we believe cordless products should last longer than the batteries they come with. That's why we don’t give robot lawn mowers Best Buy recommendations if spare batteries cannot be bought from the manufacturer – no matter how good the mower might be.

Should I buy it?

All the tests we run make up a part of each robot mower’s total test score, which is the percentage figure we award each model. Some tests are more important than others, though, and so carry different weights:

  • Grass cutting ability and efficiency 60%
  • Ease of use and convenience 20%
  • Quietness 10%
  • Instructions 5%
  • Construction 5%
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